faa3ec2304 span: Add std::byte helpers (MarcoFalke)
fa18038f51 refactor: Use ignore helper when unserializing an invalid pubkey (MarcoFalke)
fabe18d0b3 Use value_type in CDataStream where possible (MarcoFalke)
Pull request description:
This adds (currently unused) span std::byte helpers, so that they can be used in new code.
The refactors are also required for https://github.com/bitcoin/bitcoin/pull/23438, but they are split up because the other pull doesn't compile with msvc right now.
The third commit is not needed for the other pull, but still nice.
ACKs for top commit:
klementtan:
reACK faa3ec2. Verified that all the new `std::byte` helper functions are tested.
laanwj:
Code review ACK faa3ec2304
Tree-SHA512: b1f6af39f03ea4dfebf20d4a8538fa993a6104e7fc92ddf0c4606a7efc3ca9a8c1a4741d98a1418569c11bb9ce9258bf0c0c06d93d85ed7e208902a2db04e407
33c6a208a9 span, doc: provide span.h context and explain lifetimebound definition (Jon Atack)
d14395bc5d net, doc: provide context for UnserializeV1Array() (Jon Atack)
Pull request description:
Add contextual documentation for developers and future readers of the code regarding
- CNetAddr::UnserializeV1Array (see #22140)
- Span and why it defines Clang lifetimebound locally rather than using the one in attributes.h
ACKs for top commit:
laanwj:
Documentation review ACK 33c6a208a9
Tree-SHA512: cb8e6a6c23b36c9ef7499257e97c5378ec895bb9122b79b63b572d9721a1ae6ce6c0be7ad61bdf976c255527ae750fc9ff4b3e03c07c6c797d14dbc82ea9fb3a
e3e7446305 Add lifetimebound to attributes for general-purpose usage (Cory Fields)
1d58cc7cb0 span: add lifetimebound attribute (Cory Fields)
62733fee87 span: (almost) match std::span's constructor behavior (Cory Fields)
Pull request description:
Replaces #19382 with a different approach. See [this comment](https://github.com/bitcoin/bitcoin/pull/19382#discussion_r446332852) for the reasoning behind the switch.
--
Description from #19382:
See [here](http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0936r0.pdf) for more detail on lifetimebound.
This is implemented using preprocesor macros rather than configure checks in order to keep span.h self-contained.
The ```[[clang::lifetimebound]]``` syntax was chosen over ```__attribute__((lifetimebound))``` because the former is more flexible and works to guard ```this``` as well as function parameters, and also because at least for now, it's available only in clang.
There are currently no violations in our codebase, but this can easily be tested by inserting one like this somewhere and compiling with a modern clang:
```c++
Span<const int> bad(std::vector<int>{1,2,3});
```
The result:
> warning: temporary whose address is used as value of local variable 'bad' will be destroyed at the end of the full-expression [-Wdangling]
Span<const int> bad(std::vector<int>{1,2,3});
```
ACKs for top commit:
sipa:
ACK e3e7446305
ajtowns:
ACK e3e7446305 (drive by; only a quick skim of code and some basic sanity checks)
MarcoFalke:
review ACK e3e7446305🔗
jonatack:
ACK e3e7446 change since last review is adding `[[clang::lifetimebound]]` as `LIFETIMEBOUND` to src/attributes.h as suggested in https://github.com/bitcoin/bitcoin/pull/19387#issuecomment-650752959.
Tree-SHA512: 05a3440ee595ef0e8d693a2820b360707695c016a68e15df47c20cd8d053646cc6c8cca8addd7db40e72b3fce208879a41c8102ba7ae9223e4366e5de1175211
This prevents constructing a Span<A> given two pointers into an array
of B (where B is a subclass of A), at least without explicit cast to
pointers to A.
c31cbe7cfe Add C++17 test to Travis (Pieter Wuille)
7829685e27 Add configure option for c++17 (Pieter Wuille)
0fbde488b2 Support conversion between Spans of compatible types (Pieter Wuille)
7cbfebbf3d Update ax_cxx_compile_stdcxx.m4 (Pieter Wuille)
Pull request description:
This adds a `--enable-c++17` option to the configure script, fixes the only C++17 incompatibility (with a commit taken from #18468), and adds a Travis test for it.
This is all off by default, and release builds remain C++11.
It implements the first step of the plan in https://github.com/bitcoin/bitcoin/issues/16684.
ACKs for top commit:
elichai:
tACK c31cbe7cfe
practicalswift:
Tested ACK c31cbe7cfe
hebasto:
ACK c31cbe7cfe, tested on Linux Mint 19.3 both C++11 and C++17 modes. Compiled and passed tests locally.
Tree-SHA512: a4b00776dbceef9c12abbb404c6bcd48f7916ce24c8c7a14116355f64e817578b7fcddbedd5ce435322319d1e4de43429b68553f4d96d970c308fe3e3e59b9d1
